A goal of research focused on solution-based processes for the manufacture of solar cells is to lower the cost of generating electricity from sunlight. Transparent, conducting indium tin oxide (ITO) film represents the single largest contribution to the cost of a solution-processed solar cell, but replacing ITO with solution-coated layer of nanowires can greatly lower this cost. This presentation will show how the assembly of copper atoms can be guided in solution to produces nanowires with dimensions, and thus properties, tuned for use in transparent conducting films. Copper nanowires can be produced with a scalable, solution-based process in which they grow at ~100 nm/s through the diffusion-limited addition of a copper(I) precursor to a copper nanoparticle.  Simulations of the properties of nanowire networks reveal that maximizing the optical transmittance of a nanowire film while minimizing its electrical resistance requires minimizing the diameter of the nanowires, area fraction of the nanowires, the number of contacts between nanowires, and the contact resistance between nanowires.  This detailed understanding of the structure-property relationship of nanowire films guided the synthesis of nanowires that could be coated from an ink to create films with properties that matched that of ITO. Subsequent oxidation of copper nanowires can be prevented by coating them with a thin layer of Ni, Zn, Sn, or In.  Organic solar cells made with copper-based nanowires exhibit device efficiencies of 5%, comparable to values obtained for devices made with silver nanowire-based transparent electrodes. Cu-Ni, Cu-Co, and Cu-Pt nanowires can also be used as optically transparent catalysts for photoelectrochemical production of hydrogen.

Synthesis and processing of copper-based nanowires for use as transparent conductors

253rd National Meeting (2017)

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